Every team has their big rivals. For the New York Red Bulls, it's D.C. United. To a lesser extent, the new England Revolution, Chicago Fire, and Philadelphia Union can claim some sort of rivarly. Even the new kids in town (New York City FC) have taken a ride on the Red Bulls' hate train this year. The question is, how much do we as a fan base, hate the other teams?
Full disclosure: I stole this idea from Adam Taylor at Black and Red United (yes, it's a DC blog, they have good ideas every once in a while surprisingly).